1. Field of the Invention
The present invention relates generally to control of a printing device, and more particularly, to the control of such a device during printing in an interleaved mode.
2. State of the Art
Printing devices, such as ink jet printing devices, are well known. These types of printers are available from, for example, Hewlett Packard and ENCAD. As those skilled in the art will appreciate, ink jet printers often include at least one non-interleaved, or non-overlap mode of operation wherein no overlap of the print device over earlier printed bands occurs. Further, these devices include at least one interleaved, or overlap, mode of operation. To better assist in an understanding of the present invention, a brief review of an overlap mode of operation will be provided.
A typical ink jet printing device includes plural print heads, each of which includes a plurality of ink jet nozzles. The plural ink jet nozzles associated with a given color of printing ink can be displaced from one another in a vertical direction. In a non-overlap mode of operation, all of the ink jet nozzles are operated to print a continuous band as the print head is moved across a printable medium. Each pass of the print head across the printable medium (e.g., sheet of paper) constitutes a printed band. In the non-overlap mode, the print head is repeatedly scanned back and forth across the sheet without overlapping a previously printed band.
In contrast, in an overlap mode, the print head is controlled such that a given percentage of the print head, and thus the ink jet nozzles, overlap a previously printed band on the sheet (e.g., 25% or 50% of the nozzles in the print head overlap a previously printed band). As such, each area of the sheet is printed using multiple scans with different portions of the print head or heads. Such a technique is considered to improve the consistency of a printed image.
One drawback associated with conventional ink jet printing devices, regardless of whether they operate in an overlap mode or in a non-overlap mode, is that when one or more ink jet nozzles malfunctions, undesired inconsistencies can result in a printed image. This can be disastrous to a production run. It would therefore be desirable to provide some method and device which can account for the occurrence of malfunctioning ink jet nozzles without requiring discontinuation of the printing operation.